Pneumatic vibrator



3 Sheets-Sheet 2 W. S. BOHLMAN PNEUMATIC VIBRATOR WALTER S. BOHLMAN INVENTOR.

AGENT FIG. 8

Sept. 9, 1952 Filed Dec. 22, 1949 Sept 9, 1952 w. s. BOHLMAN 2,609,791

PNEUMATIC VIBRATOR Filed Dec. 22, 1949 5 Sheets-Sheet 3 lOl / lllll FIG. 9 WALTER s. BOHLMAN INV ENTOR.

BY Wgmm AGENT Patented Sept. 9, 1952 ,UNITED s 'lATlezs PATENT OFFICE.

PNEUMATIC VIBRATOR Walter s. Bommaafwilmingmn, Del., assignor to Hercules Powder Company, Wilmington, Del.,

a. A corporation of Delaware Application DecemlienZZ, 1949, Serial N o. 134,528

12 Claims. 1

This invention relates to vibrators and `more i particularly to pneumatic vibrators having aV unidirectional power stroke and a controllable speed of vibration at a given power.

Electricpand uid pressure-actuated vibrators have an ever-increasingscope of application. Whereavibration of` very high frequency is desired, fan electric vibrator `is generally .employed while a hydraulic or pneumatic vibrator is normally used `where a vibration of somewhat lower frequency is desired, or wheretheuse of elec- In fact,-one ofthe printricity is undesirable. cipal advantages of a hydraulicxor pneumatic vibrator over an electric vibrator lies'in the fact that although it is necessary to; vary power, a

fluid-actuated vibrator can fbemade to operate at different speeds by av simple valving mechanism situated in the feed line in-contrast to thermionicvalving or other complicated electrical means necessarytoV controlling the frequency of electric vibrators. An additional advantage lis that hydraulic or pneumatic vibratorsare substantially explosionproof and lend themselvesto applications `where explosive atmospheres Aare encounteredor explosive materials vare actually being conveyed or packed by vibration...l Y

Present hydraulic or pneumatic vibrators have the disadvantage, fhowever, that in order to alter their vibration frequency, `the -pressure of the actuating medium must be. correspondingly altered..` Such alteration is normally effected by closingor openingan ordinary globe` valve in 'the` supply line. Consequently, as the pressure of `.the actuating medium is varied toalter-` speed and/or amplitudet of vibration, the power delivered by each stroke of the pulsating piston l is correspondingly altered.` This is extremely disadvantageous where it is desiredto employ a power stroke of constant force but at differing frequencies. necessary to design a vibrator for each particular application. For example, it has been found.

that. in -using vibration for packing; different speedsoi vibration arerequired for optimum results `andgtpower economy with different materials.

As a result, it has been found` It has been-discovered that light, iluii'y substances-such as aluminum leang powder-` and soap flakes-cannot be settled in a container with a high-speed vibration, but will settle when a frequency oi'labout one hundred oscillations per. minute `is employed. Incomparisonyheayier materials, such alscciree, pack best atmuch higher-frequenciesfflt will at once be seen,...

"therefore,v` ithat even if a manufacturer pro-.-

duces only asingle commodityf but makes it in? particles of substantially diierent size anddensity, a diierent vibrator for eachy substantially different particle size and ntype must be ein-- ployed to obtain optimum performance `in terms of packing time, packing density, and power economy. Since alarge number of vibrators are economically undesirable, it has been the practice to select a vibrator having a frequency and power stroke giving fairly satisfactory packing for an average material.

While `the pressure .of the actuatingimedium of a duid-actuated 'vibrator can be diminished to reducefrequency,` the. reduced 4speedof vibration can only be obtained at a Asacrifice in the power of the individual powerlstroke. sirability of-a vibrator which operates at a constant pressure with a constant power stroke, but which may also be operated at any desired irequency up to the natural frequency of the par'- ticular vibrator, is` consequently apparent.`

Therefore, an object of the present invention is a pneumatic vibrator having a unidirecto'nalA power stroke which `may be made to `op`erate"at i variable speeds .without alteringlthle pressure .01" l Vthe actuating medium.

A further. object of the invention is a pneumatic vibrator having a unidirectional power stroke, which may be operated at variable speeds without changing the force exerted by the individual power' stroke.

An additionall object of the invention is an adjustable, automatic valve assembly for a pneumatic vibrator with a unidirectional power` stroke which will operate to interrupt/the how. of compressed air during the exhaust" stroke of' the vibrator piston an'dby which the vibration frequency` may be controlled, if desired.. l Generally described, the present 'invention -is a pneumatic vibratorhaving in combination a cas'- v ing forming fa cylinder, a` reciprocable piston dis'- i posed in the cylinder, exhaust ports located .inl the air exit passage inthe vibrator casing andthe `other .endoiwhich leadsto the atmosphere; `saidA g The dei way under the force exerted by the pressurized ari when suiiicient of the compressed a'ir is released to the atmosphere through the metering means. An additional embodiment of' the invention is a valve assembly for` a pneumatic vibrator having a unidirectional power stroke whereby y vibration frequency can be positively controlled which has in combination a casing, a first passageway through the casing having an inlet for pressurized air at one end'thereof and an outlet for pressurizedair at the other end thereof, a second passageway through the casing having an inlet for air at one end and an outlet for air at the other, said second passageway having a check Valve positioned inthe inlet to permit entry of air under pressure but to prevent a reverse now and a metering means for air disposed in the outletwhereby the flow of air through the outlet is regulated, andslidable means disposed within the valve assembly which is moveable in one direction to close the rst passageway when the force exerted by the air in the second passageway onthe slidable means exceeds theforce exerted on the slidable means by the air inthe first passageway and which is moveable in the opposite direction when suilicient of the pressure in the second passageway has been released through the metering means.

Having generally described the invention. more specic illustration of various embodiments will be given with reference to the accompanying drawings wherein reference symbols refer to rlike parts wherever they occur.V Fig. 1 is a plan View of a vibrator in accordance with a preferred embodiment of the invention. Fig. 2 is a part sectional, part elevational view vof the vibrator of Fig. l. Fig. 3 is an alternate embodiment of a portion of the valve assembly shown in Fig. 2, and Fig. 4 is a side elevation of the vibrator shown in Fig. 2. Figs. 5, 6, 7 and 8 are part elevational, part sectional views of the vibrator of Fig. 2 at different points in the operational cycle. Fig. 9 is a part sectionahpart elevational view of a vibrator .according to afurther embodiment of the invention.

Referring to Figs. l, 2,4, 5, 6, 7 and 8, and particularly to Fig. 2, a pneumatic vibrator is shown having a casing. It-forming a-cylinder A reciprocable piston I2 is positioned in cylinder An air inlet I3 to the cylinder is located in one end of the casing Ill and exhaust ports le and l5A are positioned in the casing |U at points equidistant from the ends of the cylinder Il. The exhaust ports |4 and l5 are separated by a distance equal to the length of the piston |2 so that when one end of the piston begins to cover one port, the other end of the piston will begin to uncover the other port. An additional air exit passage |63 from the cylinder I l is situated in the casing I0 at the end opposite the kair inlet port I3. A threaded plug l'l'rseals the bottom of the vibrator casing l@ which enables insertion and withdrawal of the piston I2. Y

Aflixed to the side of hte vibrator casing |l by bolts I8 and sealing gasket I9 is a Valve as- Ythe ports 276 and 2'| in the check 4 seinb1y'having a casing 20- whieh forms a chamber 2| having two sections of dinerent diameter. A recess 22 is located in the valve casing 20 amd is in communication with the air exit passage f6 the vibrator casing |0. A thread 23` is formed in valve casing 20 and extends into the chamber 2|. A recess 2 4 is formed in the wall of casing 28 opposite the thread 23. A threaded spring-actuated check plug' 25 threadedly engages the thread 23, with the base of the plug being retained in the recess 24. Check plug 25 has ports 26 and 27 located respectively in the upper and lower walls thereof. A valve 28 in check plug 25 allows the passage of compressed air through ports 2B and 27 into the chamber 2| from the recess 22 but prohibits a reverse flow. Above the check plug 25 the casing 20 is threaded to receive a threaded, adjustable exhaust valve 29. The valve 29 is adjusted by screw 3G and whenever the valve 29 is partially or fully open, chamber 2| is in communication with the atmosphere through through the valve 29.

An air inlet 3| is located in the valve casing 2|] near the closed end of the portion of chamber 2| V having the smaller diameter. A recess 32, formed inthe valve casing 20, is in communication with inlet |3 in the vibrator casing l0. In communication with recess 32 is a pas sage 33A which opens into the chamber 2| above the air inlet 3|. a continuation of passage 33. Also in communication with the recess 32 is a passage 35 which opensL into the chamber 2| at a point above passage 33. Passage 36 is a continuation of passage 35 through casing 2U to the atmosphere.

A reciprocable piston 31 is disposed in slidable, substantially air-tight relationship in the portion of the valve chamber 2| having the smaller diameter. An annular groove 3B is cut in the piston 3l' so that the groove registers with passages 35 and 36 when the piston is fully within the portion of the chamber having the smaller diameter. The distance to which the piston may extend into this portion of the chamber when inserted from the portion having the larger diameter is governed by a projection 39 on a threaded plug 43 disposed in the valve casing 20 at the base of the chamber 2|.

A piston 4| is disposed in slidable, substantially air-tight relationship below check plug 25 in the portion of the chamber 2| having the greater diameter. |The length of the piston 4| is such that when it is forced upward by the piston 3'|, the lower end of the piston 3'| is able to clear the upper edge of passage 33 and recess 34, thus bringing air inlet 3| and passage 33 intov communication. An annulus 42 is formed in the wall of chamber 2| at the point Where the piston 4| meets the piston 31 when the piston 31 is resting onthe projection 39 of the plug 4D. An orice 43 is provided in the valve casing 20 which leads from the annulus 42 to the at mosphere, thus allowing air to enter the largel portion of the chamber 2| under the piston 4| when thepiston 4| is forced upward by the piston 31. When the piston 4| returns to the position shown in Fig. 2, the air admitted on the up-stroke exhausts to the atmosphere.

Threaded sockets 44 are provided in the top of the vibrator casing Il] to4 enable the vibrator to Vbe secured to the object to be vibrated. Sockets '45 are provided in the plug to receive a Spanner for securing the plug in place.

plug 25 and Recess 34 in the casing 20 is is located in'the wall of section A near the end of cylinder 14. A recess 16 is located in the wall of section A at a point above the air inlet 15 and is in communication with the air inlet port 54 in the vibrator casing. A passage 11 leads from recess 16 to the cylinder 14 and is extended across the bore and into the opposite cylinder wall to form a recess 18. Above the passage 11 is located a second passage 19 which leads from recess 16 to the cylinder and is extended across the bore, through the casing and to the atmosphere. The lower portion of a piston 80 is disposed in slidable, substantially air-tight relationship in cylinder 14 and is' prevented from closing air inletr15 by an annular enlargement 8l which engages the end of section A. An annular groove 82 is cut in the piston 80 at a point which registers with passage 19 when the piston 80 extends into the cylinder 14 to the length permitted by the enlargement 8|. Section B of the valve assembly is a sleeve 90 which forms a cylinder 9| having a substantially greater diameter than cylinder 14 in section A. Mounted in cylinder is a hollow, open-ended piston 92, ythe walls of which are in slidable, substantiallyair-tight relationship with the walls of cylinder 9|. The upward travel of the piston 92 is restricted by the superimposed section C.

ISection C of the valve assembly contains a chamber |00 which is in communication with the air exit passage 59 in the vibrator casing 50 and contains a spring-actuated check plug |0| which admits pressurized air from passage 59 into chamber |00, but prohibits a reverse ilow. A passage |02 extends from chamber |00 to meet a passage |03 which vents to the atmosphere. Disposed in the passage |03 is the needle l|54 of needle valve assembly |05 which is capable of completely shutting on? passage |03 or leaving it open to the desired degree. Chamber I 00 of section C is in communication with cylinder 9| of Vsection B through port |06. Check plug |0| is inserted into chamber |00 and retained therein by a threaded plug |01 in the wall of the valve casing 90.

The operation of the vibrator of Fig. 9 is substantially identical to that described in the preferred embodiment. To begin operation, the needle valve |05 may be left open or may be adjusted to a predetermined setting. The incoming air passes through inlet into the end of cylinder 14 and forces pistons 80 and 92 up until passage 11 is brought into communication with the air inlet 15. The air then passes through passage 11, through recess l0 and inletport 54 into annular groove 53 and down duct 51. to the base l is compressed in the upper portion of cylinder 5 l.V

The check plug 0| is forced backward into chamber |00 and the compressed air admitted into chamber |00 passes through port |06 into cylinder'Sl where it exerts pressure on piston 92. Piston 92 is depressed and piston S0 is thus forced downward to interrupt the iiow of incoming air. The piston 00 is forced upward by the pressure of the incoming air when suicient of the pressure above the piston 92 has been bled oi to the atmosphere through the exhaust valve |05. Consequently, the vibration frequency of the vibrator shown in Fig. 9 may be readily controlled without any change in the eiective force of the individual power stroke of the piston. An additional feature of this particular vibratoristhat it will runat its natural frequency when-the lexhaust valve |05 is opened completely since the piston 80 will then never be depressed and the air to the base of piston 52 is cut off when the duct 51 is out of communication with annulus 53.

In case it is desirable to reverse the direction of the power stroke of the vibrator shown in Fig. f

9, a plug is placed in duct 51 and the plug is removed from duct 58. lAlternatively, the plugs may be left as shown and the piston may be removed and inverted. The entire valve assembly 10 is then removed and the passage 59 and the air inlet port 54 are suitably plugged. The plugs are removed from the alternate air exit passage 60 and from the alternate air inlet port 6|. The valve assembly is then inverted and secured to the opposite side of the vibrator casing so that chamber |00 is in communication with the alternate air exit passage 60, and passage 11 is in communication with alternate air inlet port 6|. The plug 68 is removed from the end of member 66 and the member is connected to an air line, not shown. Preferably the air line should be equipped with a valve by which the amount of pressurized air admitted to the bore of member 66 may be controlled. Only suicient pressure should be applied to piston B1 to enable it to raise piston 52 against the force of gravity.

Operation of the vibrator of Fig. 9 with a reversed power stroke is identical with the normal operation above described except for the means provided to return the piston to the top of the cylinder against the force of gravity. The piston E1 reciprocates with the vibrator piston forcing the vibrator piston up against the force of gravity and being driven downward during the vibrators power stroke. The air actuating the piston should be regulated to the minimum required to raise the piston and in this way, the retardation of the vibrator piston during the power vstroke is negligible.

It is preferred that the exhaust ports of the vibrators of the invention be spaced evenly from the ends o f the vibrator cylinders and that these ports be separated by a distance substantially equal to the length of the piston. With this arrangement the best results are achieved both from the standpoint of smoothness of operation and economy of air. However, this preferential arrangement is not essential to the operation of the vibrator. As long as the port being uncovered by the piston during the power stroke is located far enough from the end of the cylinder to enable the piston to gain sufficient velocity, the momentum of the piston will insure completion of the stroke even though the port is open during the last portion of the stroke. When the piston is returned to its starting point, either by gravity or other means, the port should be located close enough to the Vend of the cylinder to allow most of the air to exhaust and thus give a substantially full stroke. The'auxiliary exhaust means shown in the drawings is helpful in this regard.

The exhaust port being covered by the piston` during the power stroke should be placed close enough to the opposite end of the cylinder to allow the piston to make a substantially full stroke but should be located far enough from the end of the cylinder that enough air is trapped and compressed in the end of the cylinder to fully depress the valve piston or other slidable means in the valve assembly. All of these factors must be coordinated to give optimum results in each particular design and size of vibrator in accordance with the invention.V

It is preferred that two rseparate but coacting pistons be employed in the valve assembly as illustrated in the drawings. A single piston havisi'noti preferred' because thefsingle piston` is more diicultL 'tolap to the substantially air-'tight t 'necessary to` satisfactoryoperation of the valve igive' the optimum number :of i koscillations""per minute ofanydesired force `within the structural limitations of` thevibrator.' 'If'einployed in feeder andconveyor applications, the "nidirectio'nal *stroke and" control'offrequencymake "it Dpossible Ltofchoose the power-necessaryand thenieadily control the "direction" "and `'speed'of "movement "Ifusedjto` prevent clogging ^or hoppers 'andjbins vthe `-iiexiloility or control `overv frequency makes `it'iipossible to obtainfthe desired-results-while employing a 'frequency and `powerfwhich""tari the structure with `which VVthe vibrator` is employed as `little 'as possible-V` Many other advantages 'and additional modifications which4 do j not `depart from l'the scope of the"y invention' willfbecome 'apparent to 4thoseskilledinthe' ait" Itis, therefore, intended that theinvention be limited only byithe scope-of the appended claims.*

WhatI claim and `desire to protect by Letters Patenti-sy m: \r` di l i s i V--1.-A pneumaticvibratorhavingiin` combination forming acylinder,*areciprocable piston disposed in' the cylinder,- e'xhaust ports located in the casingcadj'acentthe -oppositef'ends 'ofthe cylinder; ran air rinlet `for `pressurized air lef-rding jto one endoi* the cylinder;r an air exit 'passage for 'airjcompressed by thepiston leadingA fromthe opposite' end-fof thecylinder; and a valve' assembly'said valve assembly `having in combination a rst passageway therethrough-whichis in combly Awhich is movable inone direction to close the rstpassageway under the force exerted by the compressed air admitted tothe second passageway through the'check valve and which is movable in `the opposite directionto` open the rst passageway under the force exerted bythe pressurized air when sufficient ofthe compressed air isreleased to the atmosphere through the meteringmeans. j J

2; "A' pneumatic vibrator having in combination a casing forming a cylinder, a reciprocable piston disposed in the cylinder, exhaust ports located in the casing adjacent the opposite ends of the cylinder which are separated by a distance substantially equal to the length of the piston, an air inlet for pressurized air leading to one end of the cylinder, an air exit passage for air comf'aridtiie other" tiefer 1 whi'chleads` to the' atmosphere, said'second passageway having a check valve 'at the'eiid thereof which registers) vvith "tlfiearexitA `pSSa'g and-A a ineterirlg` rrias for air at theend thi'eof Ieadingt thtniospliere; a chamber disposed in the ,valve assembly" which has two' portionsofdi'iernt"diametr,"the portion of smaller 'diameter'intersecting the rst vpassageway,"'and'"the4 'se tion ofjlarger'diameter tem-g; in `ccinmjiinic"atijojii -vvitii the second passageway at point between the Vclieclifvailve and `fmetering means; jfand"'1"eciprocablei meansl dis- "posed'in the chamber havingfsections'of vdiieren't diameter which""regi'ster with the wallsof the chamber in "substantially "air-tight relatonship said means being movable in one' direction "to iclosetheiirst passageway' under the 'forceexerted by the compressed air" admitted,` to the'second passageway through the oheckvalve' and being movable `in the opposite direction `toopen the rsti'passageway Aunder the force exerted by the pressurized air when suificientpf thecompressed 'air-is released to the atmosphere through the meteringmeansiff' "j j f 3: A-vibrator according'to claim 2in which vthe reciprooable lmeas' disposed in" the'chamber of the alve` assemblyl consists of` `two separate pistons.. ion-iii 11.2.? f f .i A-J. im

- v4." A- pneumatic vibrator" having in combination a casing formingA a cylinder, a reciproca-'ble 4piston disposed: in the fcylinderf'exhaust portsV located inthe leasing"adjacentftheopposite ends of 'the cylinder*whichI areseparated byV a distance substantiallyequalto'fthe ulengthjoffthe i piston; an airvinlet for* pressurized air f'leading to4 one "end o#thevcylindrkanairiexit passage for air compressed` by the" piston leading- Afrom the opposite end 'of-1 the cylinder, and a valve assemblysaid valve assembly y'having in Voombination a valve casing forming'a-valvechamber having two portions offdifferent jdiameter: an'air inlet-port for admission offpres'siirizedf air to 'the-end of the valve chain-berbattling-the smaller diameter, said port' being communication through-"the valve chamber with theffvibratorinlet' port; a portadjacent-tothe; end`'ofy-the portion ofl the" valve chamber having fthe greater" diameter; saidJ port contaninga check'valve and being in communication With the vibrator air exit-fpassageA said checltvalve allowing compressed air to pass from tiiefv-ibrtitorfeyiiiieerfinto the valve cylinder mit prohibiting aieturi flow;` anoutletport Ilocated adjacent Vto' theend ofthe portion of the valve cylinder rvhaving'-"t'h'e greater diameter,- said port cont'ainin'glan adjustable eXhaustjvalve; `and aV reciprocable'fpistonmounted inthe -valve chamberf-fsaidY piston having" sections of two dier'ent diameters which register with the differentiai diameters of thef'valve chamberin slidable, substantially air-tight relationship, said piston being movable in one direction to shut off the flow of pressurized air from the air inlet port of the valve assembly to the air inlet port in the Vibrator casing when the force exerted by the compressed air on the large end of the piston exceeds the force exerted on the small end of the piston by the pressurized air, and movable in the opposite direction to allow said flow of pressurized air when suicient of the pressure on the large end of the piston is relieved through the adjustable exhaust valve.

5. The vibrator of claim 2 in which a passage is provided in the valve casing which leads to the atmosphere from a point in the chamber wall adjacent to the point of juncture of the two 11 sections of the piston at the time when the piston is at its limit of movement into the portion of the valve cylinder having the smaller diameter, said passage allowing atmospheric air to enter the valve cylinder under the large portion of the piston when the piston is moved in the opposite direction.

6. The vibrator of claim 2 in which an auxiliary exhaustv means is provided'for exhausting air from beneath the vibrator piston during its exhaust stroke, said means `comprising a passage in communication with the air-inlet port in the vibrator'casing and which passes through the valve casing at a point about the air inlet port located in the portion of the valve cylinder having the smaller diameter, and rwhich registers with an annular groove cut in the valve piston when the piston is at its limit of movement into the portion of the valve cylinder having the smaller diameter.

7. A valve assembly for a pneumatic vibrator having a unidirectional power stroke whereby vibration frequency can be positively controlled, which in combination has a casing, a rst passageway through the casing having an inlet for pressurized air at one end thereof and an outlet for pressurized air at the other end thereof, a second passageway through the casing having an inlet for air at one end and an outlet for air at the other end, said second passageway having a check valve positionedin the inlet to permit entry of air under pressure but to prevent a reverse flow and a metering means for air disposed in the outlet whereby the flow of air through the outlet is regulated, and slidable means disposed within the valve assembly having the ends thereof in substantially iluid-impervious relationship with each other, the end thereof disposed adjacent the second passageway having a greater diameter than the end thereof disposed adjacent the first passageway, said slidable means being moveable in one direction to close the rst passageway when the force exerted by the air inthe second passageway on the slidable means exceeds the force exerted on the slidable means by the air in the first passageway and which is moveable in the opposite direction when sufficient of the pressure in the second passageway has been released through the metering means. k

8. A valve assembly vfor a pneumatic vibrator having a unidirectional power stroke whereby vibration frequency can be positively controlled, which in combination has a casing, a first passageway through the casing having an inlet for pressurized air at one end thereof and an outlet for pressurized air at the other end thereof, a second passageway through the casing having an inlet for air at one end and an outlet for air at the other, said second passageway having a check valve positioned in the inlet to permit entry of air under pressure but to prevent a reverse ow and a metering means for air disposed in the outlet whereby the flow of air through the outlet is regulated, a chamber disposed in the valve assembly which has two portions of different diameter, the portion of smaller diameter intersecting the rst passageway, and the portion of larger diameter being in. communication with the secondpassageway atV a point between the check valve and metering means, and reciprocable means disposed in the chamber having sections of different diameter which register with the walls of the chamber in substantially air-tight relationship, said means being moveable in one direction to close the first passageway when the force exerted on the end of the section having the larger diameter exceeds the force exerted on the endrof the section having the smaller diameter by the air in the rst passageway, and being moveable in the opposite direction by the force exerted onthe end of the section having the smaller diameter to open the rst passageway when sufficient of the pressure in the second passageway has been released through the metering means. l

9. A valve assembly according to claim 7 in Whi-ch the reciprocable means disposed in the chamber consists of two separate pistons.

10. A valve assembly according to claimf in which a passage is provided in the valve casing which leads to the atmosphere from a point in the chamber wall adjacent to the point of juncture of the two sections of the piston at the time when the piston is at its limit of movement into the portion of the valve cylinder having the f smaller diameter, saidpassage yallowing atmospheric air to enter the valve cylinder under the large portion of the piston when the piston is moved inithe opposite direction.

ll. Alvibrator according to lclaim l in which a huid-actuated piston is slidably mounted in the end of the vibrator cylinder at which the vibrator piston completes its power stroke, said Huid-actuated piston being in longitudinal alignment with the vibrator piston.

12. A vibrator according to claim 4 in which a fluid-actuated piston is slidably mounted in the end of the vibrator cylinder at which the vibrator piston completes its power stroke, said fluid-actuated piston being in longitudinal alignment with the vibrator piston.

WALTER S. BOI-ILMAN.

Country Date Y Germany Oct. 6, 1932 Number 

